In our case, we were using postfix via iRedMail and every incoming mail had a delay around 7 minutes. The problem was fixed by disabling the chroot operation in the settings.
Edit the file /etc/postfix/master.cf
It probably looks like this
# ============================================================= # service type private unpriv chroot wakeup maxproc command # (yes) (yes) (yes) (never) (100) # ============================================================= smtp inet n - - - - smtpd
Change it to
# ============================================================= # service type private unpriv chroot wakeup maxproc command # (yes) (yes) (yes) (never) (100) # ============================================================= smtp inet n - n - - smtpd
Now restart and reload the postfix mail server and you’re good to go.
[root@mail ~]# /etc/init.d/postfix restart Shutting down postfix: [ OK ] Starting postfix: [ OK ] [root@mail ~]# /etc/init.d/postfix reload Reloading postfix: [ OK ]